The Mistake To Not Make
by SoDeSi47
Summary: Alec Lightwood has a decision to make, but it's not going to be easy. There's two choices available, and he has to pick one of them—but he won't be able to switch. Will he see what's waiting patiently right in front of him, or will he keep endeavoring to peer past the obvious to someone he knows he will never be able to have, but he can't let go of? Oneshot Magnus/Alec


_Alec POV_

"Alec, don't do this."

Magnus' voice drifted up to me in the rafters. He was currently standing on the mat in the training room at the Institute, his yellow-green eyes sparkling like the glitter he wore as he craned his neck to watch me. Just looking at those eyes made the supporting tendons in my knees suddenly disappear, but that probably wasn't very good right now.

Why? Well, I was currently about thirty feet above solid ground, balancing on a beam that ran across the ceiling of the room.

So I could goggle at Magnus' eyes later—right now I just had to focus on not falling. Although, it was kind of hard to turn a blind eye to Magnus when he was wearing neon overalls on top of a striped blue and white shirt with puffy sleeves. Not to mention the baseball cap, that would've looked normal if not for the fact that Magnus had done something to make the cap extend into a loop that went up and over like a perm during the 80s.

"I'll be fine," I said, but I didn't know if I was reassuring him or myself. "I've done this before."

"Have you ever landed it?"

I didn't answer him, instead I stood up straight, looking down at the ground while taking a deep breath. An inchworm of worry started creeping it's way into me, traveling up to my brain and overtaking my ability to think correctly. The brutal truth was, even though I could fight pretty well and kill demons and draw some amazing runes, I wasn't very fond of flips. I could never get them right. Jace looked like he was born to do it while holding a couple damsels in distress at the same time and still executing the perfect flip, landing on both feet with cat-like grace.

But that was Jace. And I was . . . well, me. No matter how many times I wasn't satisfied with it, I couldn't really change myself in that big of a way.

However, I had to do this. But it was hard. Just think about it: one flip, spinning as I did so, and landing gracefully like that weird dude in a red and blue leotard the mundanes liked to call "Spiderman" or whatever. Well, I'd like to see _him_ face a horde of demons with poisonous saliva and razor-sharp claws. We'll see how Mr. Spiderman does then, huh?

"Alec, really, I don't know why you're doing this."

I peeped over the edge down at Magnus. "I just need to practice, no biggie."

"Well, I have a feeling that when you're splattered down on the floor like a bag of red confetti, it won't be a 'no biggie' anymore."

Sending a withering look down at him, I replied, "Oh, thanks for the vote of confidence. And the lovely mental image you just engraved in my brain."

"You'd make a lovely color. Maybe when you're dried up, I could sprinkle you on my new outfit I just got, add an autumn feel with the rusty color," he mused, almost as if talking to himself. That idea was so repulsive that I just stared down at him for a couple seconds with my nose wrinkled up.

The warlock pursed his lips, then shook his head. "You're right. I don't think red is my color."

"Anyway," I said, my eyes widening a fraction for a millisecond. "Stop distracting me. I need to focus."

"Just like I need a new rainbow headband; and Isabelle needs to get rid of those horrid azure high heels; and the United States of America needs to pay off their debt." Magnus gave me a pointed look. "Not everything happens, dear."

An irritated sigh escaped my lips. "By the Angel, Magnus, just please let me do this."

Magnus stepped back, holding out his hand. "Be my guest."

I took a deep breath once more, shaking out my shoulders. The unnamed dagger at my side clanked against my thigh, the light tapping nothing compared to my pounding heart. I was surprised Magnus hadn't heard it and commented yet.

Inhale. Exhale. I had to make this. I could do it.

Inhale.

Magnus watched me, thirty feet down on the ground, and my sight was starting to blur. I forced myself to look straight, squinting to focus and trying to ignore the length between me and the ground.

Exhale.

Here goes nothing.

With a powerful push from my hamstrings, I leapt off the rafter, tightening my limbs to my body to streak through the air like a diving hawk. Well, I _wanted_ to look like a hawk—but I bet I had a striking similarity to a falling duck.

They say time slows down when you are about to die. You feel like you are watching a movie in slow-motion, starring you and your immediate death, forced to see every excruciating detail. So I didn't know how to take it when I felt my surroundings stop going by so fast and slow so I could see what was happening clearly. But I didn't have that much time to dwell on it.

In a desperate attempt, I twisted my body, hoping to at least do the backflip I had planned with a three-sixty twist. However, it didn't look like luck was on my side. I managed to get myself turned around so that when I landed, it would be flat onto my stomach. That might hurt.

The ground hurtled to me menacingly quickly. I was proud I didn't scream like a girl or anything, just faced my impending doom with a horror-filled silence. In my peripheral vision, Magnus in his bright suit stood out like a candle in darkness as he he was positioned against the subdued colors of the wall behind him.

Just before I was sure I was going to hit the floor and become—as Magnus so poetically put it—a bag of confetti, I saw a spark of blue, and my body jerked to a stop—a foot away from the ground. My heart felt like it was trying to beat it's way out of my throat, which was where it was now residing.

I was pretty sure I heard a sigh, then whatever invisible force that was holding me up clicked off, and I fell into a crumpled heap onto the mat. I tasted the old sweat on the ground, and grimacing, I rolled onto my back and stared at those cursed rafters above. Taking a gulp of oxygen, I cursed at my failure.

A head appeared in my vision—one with twinkling slitted eyes that looked down at me with an expression that was half-exasperation and half-adoration. Magnus chuckled slightly, the corners of his eyes crinkling as he held out a hand. Groaning, I reached my own hand up and grabbed his, trying to keep the butterflies in my stomach calm at the touch. I mean, seriously. All we did was touch hands, and that still was enough to make tingles go through me like I had touched an electrical socket.

"That sucked," I stated dejectedly as I was standing next to Magnus, the warlock playing with the blue flame of his magic. I watched as it spread out like a web across his fingertips; it never ceased to amaze me.

"It wasn't too bad," he said. "The flip you did, if you had carried it out, would almost be a perfect pirouette in the air. You could take up ballet—you can always teach an old dog new tricks."

I rolled my eyes. "It's 'you _can't_ teach an old dog new tricks', Magnus. But thanks for the encouragement. And for—you know—saving my life."

"Oh, it's no biggie." He smirked as I glowered at him for using those two words.

He and I started walking back to the entrance of the training room, me rubbing my back where I think I pulled a muscle. Our muffled footsteps echoed off the edges of the large, empty room. At the moment, nobody else was in the Institute. Isabelle and Jace had gone off with Clary to hunt more demons or find more clues and whatnot. I had been trying to catch up on my studies when I looked up to see Magnus watching me across the room.

"Oh, my God!" my voice exclaimed in shock as I jumped at the unexpected (but not dreaded) sight of the warlock.

"Just dropping in," Magnus had calmly stated. "Did you know that the shirt you're wearing looks exactly like one that belongs to me?"

I glanced absentmindedly at the grey and black t-shirt covering my upper body. "It is yours, I took it." It was the most normal thing in his drawers.

Magnus frowned. "Oh. Yes, that does explain it."

"What are you doing here?"

The warlock had answered that he was bored. Though, how the High Warlock of Brooklyn could be bored, I didn't understand. But I didn't question it.

For a moment, we just sat in each other's presence, then Magnus suggested that I give him a tour around the Institute. I think he just used that to start something other than awkwardly staring at one another, for he seemed to know the place I had lived at for most of my life more than I did. He kept pointing things out and saying how he didn't remember that being there or how the color matched "horrendously" with the curtains.

We soon found ourselves in the training room, and I had scampered up to try and practice a flip.

And now here we were. "So, where to now?" the warlock beside me asked with the enthusiasm of a four-year-old on a trip around a candy store.

Well, a four-year-old other than Jace. He would probably just look disdainfully down at the sugary delights as if they were a half-dead demon slobbering at his feet. He was just supercilious like that.

 _Stop that_ , I told myself sternly. _Stop thinking about Jace. You're walking with Magnus, not Jace. Just stop pining over him, for the Angel's sake_.

"What're you thinking about?" Magnus questioned curiously. If I didn't know differently, I would've thought he was mind-reader.

"Nothing," I mumbled in response. But that feeble excuse didn't work.

Magnus stopped walking. I went a few more steps before pausing like he did, a few yards away from the door.

"You're thinking about him, aren't you?" he said incredulously, making it more of a statement than a question.

"I—I don't know what you're talking about, Magnus." My voice sounded weak even to my ears.

I heard him scoff indignantly behind me, and I turned to look him square in the eyes. But before I could defend myself, Magnus started talking again. "I can't believe you sometimes, Alec. First off, he's your _parabatai_ , so you have no business having anything romantic with him—"

"There's nothing going on! I told you that."

"—and second, I'm here with you! Why are you thinking about Jace when I'm right here?"

"And what's wrong with that?" I said defensively. "It's not like you came here just for me. You said you were bored, so I was obviously the last choice of how to spend your time."

Magnus rolled his brilliant eyes, the sparkles on his eyelids vanishing for an second, then reappearing in full sight as he narrowed his eyes, looking like a thousand tiny stars glimmering above his feline eyes. "If you're utter ignorance wasn't so damn endearing, I would have no idea why I was here."

My eyebrows furrowed. "What?"

He sighed, then said suddenly. "What do you think of me?"

This time, my eyebrows rose instead. " _What_?" I repeated, but my voice was an octave higher.

Magnus looked like he was resisting the urge to send his eyes skyward once more. "I meant, if you had to call me something other than 'Magnus', what would it be?"

"A warlock?" I suggested timidly.

An angry exhale came from Magnus' mouth. "Are you serious?"

"Uh, I think. I don't exactly know."

Magnus took a step towards me, then another. Soon he was standing right in front of me, his eyes looking straight through mine, going through the drawers in my brain, searching for what he wanted. "What would you call me? Just a friend? A friend with benefits, as they say?"

My mind flashed to the times Magnus and I had spent as something other than friends. Times where there was no space between us—quite literally. My lips prickled at the memories, and my breath picked up, but I tried to keep it even.

"I don't think I understand exactly what you're getting at—"

Magnus eliminated the air between us by grabbing my shirt and yanking me toward him. I stumbled into his chest, my sudden yelp cut off by Magnus' lips pressed against mine. As it always happened, my breath disappeared, along with my ability to think straight, as I melted into Magnus.

But just as quickly as it happened, it stopped.

Magnus pulled away, his breath as labored as mine. I was left, yearning for more, my knees suddenly turned into jelly.

"Does that clearly enough demonstrate what I was implying with my question?"

Breathlessly, I nodded.

"Well, feel free to answer. But, you know, _no biggie_."

I didn't even glare at him this time. My mind couldn't focus on one thought. One minute I can't even form a single word, the next so many feelings and words and images are flooding my brain, I was in danger of drowning.

"I—I don't know, Magnus," I managed to say.

He threw his hands up, the dazzling overalls shifting as he did so. "You're so impossible, you know that? You'd think after three hundred years of living, I'd be able to read people like an open book. But no—you always seem to perplex me, Alec."

"I just . . . I can't stop thinking about Jace."

Magnus' eyebrows went up again. "Well, I could knock your head pretty hard with a wooden stick, then thoughts of Jace might leave. Oh, but wait—that wouldn't work. I bet the golden wonder-boy still appears in your dreams." The cutting sarcasm in his voice made me cringe.

"Magnus—"

"I mean," the warlock continued, not letting me speak, "don't bother about me, the warlock who's been investing most of his time in you and your friends. I could've taken a trip to Djibouti, but I decided to stay and help you Shadowhunters with the war—another thing that used to be a big no-no for me. So tell me, why am I wasting all my time on this if you don't even care one bit?"

"But I do care!"

"Well, it certainly doesn't appear that way, Alexander."

"What can I do to prove it? By the Angel—does almost falling to my death trying to impress you not tell you enough?"

The warlock raised his eyebrows. "So that's why you did the suicidal jump?"

"Well, it sure as hell wasn't because I'm good at it. As you can see, I'm not." I stopped my rush of words, counting to ten before I replied in a more controlled tone. "What can I do to prove it?"

"That's a very good question, Alec. One that I think you have to answer for yourself."

I bit back a scream of frustration. "I don't even know what . . . you and Jace—I can't—"

"Decide?" Magnus offered, crossing his arms. How he managed to look superior in that suit beat me. I would've looked like an overdressed clown—just more gaudy.

I ran a hand through my choppy dark locks, turning to pace back and forth. My mind was a whirlwind of thoughts. For so long, Jace had been the only one I had felt anything for. Then this warlock came along with his crazy outfits and glitter in the abundance, and instantly I was interested. I don't know how interested, but I was nonetheless. It was weird, seeing as he was the complete opposite of me. But, as they say, opposites attract, right?

"Just tell me the answer to one simple question." I looked at Magnus as he said that. His face was unreadable, but his eyes glinted with a fire that I knew if he stopped holding it in, all hell would break loose.

"And that is?"

Magnus stared at me for a second before answering, his gaze unnerving. It was so forceful and strong I seemed to lose all my strength, and my breath just wouldn't catch up.

"Do you care about me, or are you just using me as a distraction from Jace—the boy you can never have?"

That knocked all the breath out of me like a physical blow, and for a second I stood motionless, staring at him.

To be honest, I didn't know the answer to that. In the beginning, that might have been my reason for messing around with Magnus. If I couldn't have Jace, I might as well be in misery with someone else.

However, as I thought of it, I realized how incredibly selfish that was. Did I ever stop to think about what Magnus felt? No, not really. I never dreamed one of the most powerful warlocks in the world would become attracted to me, a Shadowhunter who couldn't even perform a simple flip.

"Do _you_ care?" I asked suddenly, feeling the unbearable need to know. "Would it matter what my answer was?"

Magnus pondered this, his eyes slitted. "Yes."

I didn't know how to take that answer, so I just replied as best as I could, straight from my heart. "Magnus, you know that . . . that two guys . . . well, it's frowned upon by the Shadowhunters and the Clave. But that never stopped me from—from loving Jace." Magnus' face tightened momentarily, then it was erased, and his countenance was as blank as a new sheet of paper. But I wanted to see an emotion in him, any kind, so I grabbed my thoughts and formed them into crayons, ready to try and draw something. "And then I met you. Right when we started all . . ." I gestured around us, encompassing the room but meaning just everything between me and him, which was bigger than any room in my opinion. "All of this—I hadn't expected it to go somewhere. But Magnus, it did."

His eyebrow rose, and he waited, still not moving. I took a deep breath.

"Maybe some part of me will never stop loving Jace. But—" I sighed. "I can still love another person." I paused, my words not coming out right. Jace could speak so well—it was like he took everything he was feeling and mashed it into a sentence so ordinary, but it held so much. Here I was, fumbling over my words like I was in a dark room full of Legos. It was just as painful, too—trying to convey all these feelings to Magnus.

"Magnus, I just need time."

The man standing a few feet away let out a pent up breath, watching me. He looked so young and angst-ridden it was hard to think of him as an immortal and powerful warlock.

"Okay," he said, letting out another big breath. "Okay, then. I'll go."

He and I stared at each other for a moment longer, then he tore his gaze away, starting for the door. But he had to pass me, and I couldn't let him go without one more kiss.

As his arm brushed by me, I turned and grabbed it, shoving him roughly back, back, and back. He hit the wall, and I pushed him into it, framing his face with my hands as I leaned forward, connecting his lips with mine.

Magnus was shocked at first, but he hesitantly leaned into the kiss, bringing his arms up to wrap one around my neck, then entangle his other hand into my hair. His hat fell off, letting his long strands of black hair fall in a cascade around him. It was silky, feeling like water beneath my calloused Shadowhunter hands. I let out a surprised noise in the back of my throat when Magnus suddenly yanked us both around, slamming me into the wall so he was in charge. Our kiss was fierce yet languid, desperate yet relaxed. I never felt as elated as I did when I was with Magnus, my mouth moving against his, our lips fitting perfectly together like two puzzle pieces. He bit my lower lip, and I murmured his name.

Then the warlock leaned back, looking deeply at me with those eyes as bright as a flashlight in the night. His head started to come forward, but it was agonizingly slow. With an annoyed and anxious snarl, I tried to kiss him, but he held me back, his hands in a strong grip at my shoulders.

"Please, Magnus," I whispered, burning with desire.

"No," he said, shaking his head. "You said you needed some time, Alec." He stepped back, releasing me. It was all I could do to not jump him again. "And time I will give you. I don't want to just be around for your beck and call, to be the person you use only to relieve your stress. I can't do that, or you'll become closer to me than I've already let you be, and that's bad enough. Unless you're going to show something more than just using me, I'm just going to try and forget you, Alec. But it'll be hard. I'll be waiting." With that, he leaned forward, placing a gentle kiss on my forehead, the complete opposite of the raging fire we had just displayed. This was just a small flame, and depending on what happened, what I chose, it could blaze up into a mighty inferno, or it could dwindle, eventually fading into nothing and killing every hint of possibility.

Magnus gave me one last gaze, full of unspoken words, then he slid past me, out the training room door and into the hall. A second later, he was gone from sight, leaving me leaning against the wall, unable to hold myself up. The burst of strength I just had had vanished. I was left being only Alec, not Alec with Magnus. It was amazing how much stability that warlock gave me. I didn't even notice it until now.

I also realized something else.

For so long, I had been staring at a locked door—Jace on one side, me on the other. I knew I couldn't get in, I knew it would never work, but I just sat there anyway, allowing nothing to penetrate my focus on that one door.

But another door had recently appeared—a vibrant and vivid one that was unlocked. One that was apparently waiting for me. My eyes had been concentrated on a different door, and I had almost missed out on the new one.

Do me a favor, will you? Stop going after someone you love but can never have. It's hopeless, not to mention useless. You can do better, with someone who is waiting to return the love you give them. Just open your eyes to new possibilities, let them expand farther than the small focus you had on one person. It will change your perspective. If you just keep your gaze trained on that one opportunity, you'll soon find out you've made a mistake by doing that—and it will be too late. Don't do it.

I decided to follow my own advice, and with one last, long look at the locked door, I turned. Everything in me shifted, and my direction was now leading me to that other door, toward the warlock that I had let into my heart.

All I needed was that one step—the first step. That step was the hardest. It was the realization that you were actually moving on, and that things might become different and maybe even uncomfortable. But in the end, it's the right decision.

Taking a deep breath, I picked my foot up, moved it forward, and let it fall.

The first step.

* * *

 **Hope you enjoyed it! I've never written a Mortal Instruments fanfic, so feedback and constructive criticism is welcome. Thanks for reading! :)**


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